This invention relates to the field of assisted walking for handicapped persons. Such persons may have become paralyzed or partially paralyzed as a result of accident or physiological disorder. Early work in this field concentrated upon walking assistance for persons who were only partially disabled. Typical teachings along that line are set forth in Keegan U.S. Pat. No. 3,083,712, in Frank et al. U.S. Pat. No. 3,204,637 and in Offner et al. U.S. Pat. No. 3,344,792. These references generally teach stimulation of relatively few muscles in a single leg.
Somewhat more recently walking assistance systems have included means for stimulating groups of muscles in both legs as shown in a paper entitled "Programmed Six-Channel Electrical Stimulator for Complex Stimulation of Leg Muscles During Walking," Strojnik, et al. IEEE TRANS on Biomedical Engineering, Vol. BME-26, No. 2, Feb. 1979, pp. 112-116 and in another paper entitled "Gait Restoration in Paraplegic Patients: A Feasibility Demonstration Using Multichannel Surface Electrodes FES," Kralj et al. Journal of Rehabilitation R&D, Vol. 20, No. 1, 1983 (BPR 10-38) pp. 3-20. These systems generally assist walking by stimulating the leg muscles on an open loop basis. That is, stimulation command signals are not adjusted in accordance with measured observations of leg movement.
Stimulated walking under full closed-loop computer control is taught in a paper entitled "Feedback Control System for Walking in Man," Petrofsky et al. Comput. Biol. Med. 14:135-149, 1984 and in a paper entitled "Computer Controlled Walking in the Paralyzed Individual," Petrofsky et al., Journal of Neurological and Orthopaedic Surgery, Vol. 4, Issue 2, July 1983, pp. 153-164. The systems described in the Petrofsky et al. papers utilize stimulation devices of the general type described in Petrofsky et al. U.S. Pat. No. 4,492,233. While such systems have been successfully tested, they are extremely complex and have produced walking only for relatively short distances under controlled conditions.
Electrical stimulation has also been used to produce swing-gait type walking. Such walking is accomplished with the aid of crutches. In practicing this technique a standing position is achieved with the body weight resting on the crutches. Then the knee extension muscles and the hip extension muscles are stimulated to enable the legs to support the body weight. Once stimulated standing has been achieved, the crutches are extended forwardly. The person's weight is then shifted to the upper body through the crutches, and the two legs are then swung forwardly to a new weight bearing position. It is apparent that such a walking gait is quite unnatural and very tiring to the upper body muscles. A typical application of this type is described in a paper by Holle et al. entitled "Functional Electrical stimulation in Paraplegics," Orthopedics, July 1984, pp. 1145-1155. Such systems have enabled walking for only relatively short distances.
Another technique for assisting handicapped persons to walk utilizes reciprocating braces as described in a paper entitled "LSU Reciprocating Gait Orthosis", Douglas et al. Orthopedics, 6:834-839, 1983. The Douglas paper describes an orthosis which supports both legs through an interconnected pair of cables. This system is used by handicapped persons without electrical stimulation of any type. The cables link the hips so that shifting of the weight and tucking of the pelvis causes the hips to initiate a walking gait. These braces have proven quite successful in allowing gait restoration in children and adults with cerebral palsy, MS, and a number of other neuro-muscular disorders. For spinal cord injured patients, the reciprocating braces offer stability and balance. However, for spinal cord injured patients with total paralysis there is a great deal of difficulty in both standing and sitting as well as in walking because power must come totally from the upper body muscles. Further, the lower body muscles are not used during walking with these braces, so there is no prevention of muscle atrophy and bone demineralization.
It is therefore seen that there is a need for an improved walking assistance system for handicapped persons.